Dengue proposal

Considerations for design of the phase II follow up

Background

• DPSEEA was used to introduce the notion of urban ecosystem health.

• The framework was applied to chronic aspect of urban conditions in Cayo Hueso.

• Participatory approaches were used to define key indicators.

• The findings:» Measurable improvements in subjective indicators. » Inconclusive change in more objective indicators.

Follow on research for dengue

• Reapply the phase I methods again.• Elaborate on DPSEEA introducing:

» the importance of context,» ecosystem processes and their interactions» Broader ecosystem health/integrity perspective.

• Refine the indicators:» learning why there is a gap between the subjective and objective

outcomes.

• Create a new decision-making and evaluation framework emphasizing learning objectives and adaptive management:» Dengue is an episodic risk in Cuba. Monitoring and intervention for

such problems are not the same as those of a chronic issue such as housing.

Lessons from Phase I

• Relative importance of exogenous factors.

• Challenges in attributing effects to intervention without a “control” population.

• …

Opportunity in Phase II

Design Feature Retrospective study

Prospective study

Indicators yes yes

Monitoring strategy no yes

Intervention strategy no yes

Learning & Adaptive management

no yes

The bigger picture

Housing

Water

Solid waste

Liquid waste

...

Chronic issues

Vector borne epidemics

Water borne epidemics

Air borne epidemics

Extreme weather

...

Acute issues

Social cohesion

Community pride

Healthy environment

Individual security

...

Psycho-social issues

CommunityHealth

Why does an overallframework matter?

• Monitoring is like our eyes• Decision-making is like our brain• We cannot look everywhere• We cannot think of everything• We need to think about costs and benefits of every

monitoring and intervention action.• We need to find the efficient and effective set of

observations (monitoring) that allow appropriate actions (campaigns).

Issues in control of epidemics• Monitoring is less than perfect

» e.g. infected are asymptomatic but have viremia» Symptoms of potential infection may go mal-reported (know 5 day bed-rest

could lead to over reporting (if compensated) and under reported (if time substitution is unavailable to the patient).

• Intervention efficacy is less than perfect:» depends on social acceptance,» depends on suitability to ecosystem (e.g. “closed” buildings),» depends on being timely, which is itself reliant on frequency of monitoring

and speed of interpretation.

• Direct and intended benefits of monitoring depend on the efficacy of interventions that could be triggered by it.

• Imperfect monitoring and interventions erodes social acceptance and trust.

Three dimensions to evaluation

• Effects:» direct and intended» indirect and ancillary

• Benefits and costs:» cases of dengue and DHF» other health effects» improved living conditions, …

• Measures:» Objective, subjective» Information flow and feedback to decision making

The challenge of sustainability in the absence of a signal

The opportunity for sustainability through indirect benefits

An Ideal Policy

• Has community support.

• Has positive impacts.

• Is monitored and enforced effectively.

• Has self-righting properties.

• Has free-drivers.

• Meets more than one objective.

Take the case of dengue in Cuba:We need to identify the policy goal,

approach & constraints• Goal

» prevent dengue

• Actions:» Reduce breeding sites for A. aegypti» Eradicate mosquito population» Isolate potential infected people from healthy

• Means:» Monitoring, interpretation and dissemination of information, » Decision-making processes

• Constraints:» The time of field workers» The time of households» The cost of fumigation (money and incidental health impacts)» The implications of forced bed-rest for feverish people» Loss of public interest for participation

The overall frameworkEcology

The scientific inputSociety

Goals and values

Whatoutcome to encourage and when

How

GovernanceMonitoring

Intervention

The ecologically possible

The socially preferred

Design alternatives

monitor what?monitor how?

when to act?what to do?

Find best system

1. Mosquito habitat

2. Mosquito density

3. Disease locally

4. Disease regionally

5. Weakly active network until trigger

6. Adaptive hotspot monitoring

a)Destroy habitat

b)Destroy mosquito

c)Change behaviour

d)…

•[1 » a]

•[2 » a+b]

•[3 » a+b+c]

•[2+3 » a+b+b]

•[4 » 1 » a+b]

•…

How should the monitoring/intervention evolve at different levels of force of

infection?The iterative cycles of monitoring and intervention. E.g.:

The first 90% can be controlled through identification and elimination of the 1st levels risk factors.

The next 90% through identification of 2nd level risk factors and interventions

• The next 90% through identification of 3rd level risk factors and interventions.• The next 90% …

The rule for when to stop is determined by the whole human-vector-virus ecology. For a disease that is hard to transmit, we can stop at the level of the first risk factors. For a disease that is easily transmitted we need to go to understanding and controlling smaller and smaller risk factors.

IllnessIllness

Transmission of Dengue Virusby Aedes aegypti

Days0 5 8 12 16 20 24 28

Human #1 Human #2

ViremiaViremia

Mosquito feeds & acquires virus

Mosquito refeeds & transmits virus

A.aegypti inecosystem

Infectedhuman inecosystem

Extrinsic incubation

period(~9 days)

Intrinsic incubation

period (~7 days)

Transmission of Dengue Virusby Aedes aegypti

Viremia

Days0 5 8 12 16 20 24 28

Human #1 Human #2

Illness

Mosquito feeds & acquires virus

Mosquito refeeds & transmits virus

ViremiaViremia

Illness

A.aegypti inecosystem

Infectedhuman inecosystem

Fumigation kills

mosquitoes

Transmission of Dengue Virusby Aedes aegypti

Viremia

Days0 5 8 12 16 20 24 28

Human #1 Human #2

Illness

Mosquito feeds & acquires virus

Mosquito refeeds & transmits virus

ViremiaViremia

Illness

A.aegypti inecosystem

Infectedhuman inecosystem

Breeding site elimination

Transmission of Dengue Virusby Aedes aegypti

Viremia

Days0 5 8 12 16 20 24 28

Human #1 Human #2

Illness

Mosquito feeds & acquires virus

Mosquito refeeds & transmits virus

ViremiaViremia

Illness

Forced bedrest isolates viremia

from vector

A.aegypti inecosystem

Infectedhuman inecosystem

Research Ideas from UBC partners• Retrospective: A full evaluation (costs and benefits,

intended and unintended) of the monitoring-intervention program. » What can be learned about dengue ecology because of the extra-

ordinary setting?» A retrospective of health and environmental impacts of the control

campaign in 2002.

• Prospective: How should the monitoring/intervention evolve at different risks of epidemic? (refinement of methodology given Cuba’s special situation)

• What are the pre-requisites for introducing self reinforcing and self-adjusting elements to the process?

Outcomes, Indicators & Interventions (to be evaluated)

Indicator > critical value

Breeding site control

Larvicide Fumigation Bed rest for the feverish

Reliable water & sewage

Costs / Benefits

Spatial-temporal coverage

Breeding sites

√ √ √ √ - - √ √ √ Ex ante risk identification

Every 15 days erery place

Mosquito population

√ √ √ √ √ √ √ - Ex post risk estimation

Every week

Serology √ √ - √ √ √ √ √ √ - Costly? Slow? Travellers,

Feverish

Community participation

Builds community needs to pay off!

Only for acts with visible benefits

Deployment cost / benefit

Dengue, water quality, …

Risk to ecosystem

Risk to ecosystem

Free riders, non-reporters

HUGE benefit Definite NEED

Deployment frequency

Every 15 days

Flow related Every 15 days 5 days 10 years

C&B of Interventions:monitoring blood samples

Costs

• High cost

• May be too late for prevention epidemic

• Loss of privacy

Benefits

• Screening for other diseases & behavioural change

Weakness

• Could change behaviour in seeking medical help

Strength

• Least ambiguous test of dengue

• Prerequisite to level of concern about DHF

C&B of Interventions:destruction of habitatCosts

• Continuous effort

• High labour input

Benefits

• Cleaner environment

Weakness

• Some households will not be able to comply.

• As the vector is not eradicated but pressed for habitat it will change its behaviour

Strength

• Could contribute to community spirit if organized as a social event.

C&B of Interventions:quarantine

Costs

• Loss of work

• Familiar discord

• More babies?

Benefits

• More babies?

• Good to have a rest

Weakness

• Hosts have viremia long before they show symptoms.

• Non-compliance

• Could change behaviour in seeking medical help

Strength

• It may provide spatially specific information for concentration of effort.

C&B of Interventions:fumigation & spraying

Costs• Needs coordination of episodic

effort & opportunity cost of labour and material input

• Contamination of environment• Loss of ecosystem integrity• Human health effects

Benefits

• Destruction of mosquitoes

Weakness

• Closed houses.

• Impatient home owners.

• Poor public relations.

• Does not kill larvae

Strength

• Fast deployment

• Politically visible

• Triggers behavioural change

C&B of Interventions:reliable domestic water supply

Costs

• High investment costs

• Only part of the solution

Benefits

• Eliminates major habitats at home

• Reduced water-borne epidemics

• Better hygiene

• Saves time

• Reduces injury

Weakness

• A long lead time

Strength

• Strong public support

• Will be easier to maintain

What aspects of the ecosystem-health approach are more readily adopted, why?

• Does the approach have value if partially adopted?» Spatial and functional organization challenges?» What critical aspects are missing and why?

• Does possibility of formal risk assessment, cost and benefit estimation, … approaches impact adoption patterns? » They did not resonate to the notion of cost.» How is “value” of information get translated into something of

similar implication here?

• What would be the features of a self-righting approach?

Need to identify goal, approach & constraints

• Goal» prevent dengue

• Actions:» Reduce breeding sites for A. aegypti» Eradicate mosquito population» Isolate potential infected people from healthy

• Means:» Monitoring, interpretation and dissemination of information, » Decision-making processes

• Constraints:» The time of field workers» The time of households» The cost of fumigation (money and incidental health impacts)» The implications of forced bed-rest for feverish people» Loss of public interest for participation